Composite fibres and yarns of acrylonitrile polymers

ABSTRACT

The invention relates to a spontaneously crimping composite fibre of acrylonitrile polymers in which one of the fibre-forming component has a content of copolymerized esters up to 6% by weight and another fibre-forming component a content of copolymerized esters which is from 2 to 6% by weight higher whereby at least one of the fibre-forming components contains as copolymerized ester at least 2% by weight of isobutene-diacetate and the total quantity of the copolymerized esters in one fibreforming component does not exceed 12% by weight.

United States Patent [1 1 Lohwasser et a1.

[ COMPOSITE FIBRES AND YARNS OF ACRYLONITRILE POLYMERS [75] Inventors:Hermann Lohwasser; Alfred Nogaj; Dieter Brokmeier, all of Dormagen;Helmut Engelhard, Leverkusen, all of Germany [73] Assignee: BayerAktiengesellschaft,

Leverkusen-Bayerwerk, Germany 22 Filed: Sept. 18, 1974 211 App], No;507,174

[30] Foreign Application PriorityData Sept. 27, 1973 Germany 2348679 [52U.S. Cl. 428/374; 264/168; 264/171; 264/182; 260/795 c; 260/855 ES 511111. C1. D02g 1/00; D02g 3/00 [58] Field of Search 161/173, 175, 172;260/85.5 ES, 88.5; 264/168, 182, 17

[56] References Cited UNITED STATES PATENTS 2,682,518 6/1954 Caldwell260/855 ES X July 15, 1975 3,515,627 6/1970 Sekiguchi et a1. 161/1733,671,619 6/1972 Fitzgerald et a1. 161/173 3,719,738 3/1973 Fnjii161/173 Primary Examiner George F. Lesmes Assistant Examiner-Lorraine T.Kendell Attorney, Agent, or Firm-Plumley & Tyner 57 I ABSTRACT 5 Claims,N0 Drawings COMPOSITE FIBRES AND YARNS OF ACRYLONITRILE POLYMERSNumerous composite fibres (bicomponent fibres) based on acrylonitrileare capable of spontaneous crimping as a result of suitable selection ofthe chemical composition of the fibre-forming components and, in somecases, as a result of special processes of polymerisation, solution,spinning or after-treatment. It is thought that crimping may be due, forexample, the shrinkage tensions released by heat in the case of compoundfibres whose components contain varying amount of neutral comonomers.Among the neutral comonomers, those preferably used on account of theirdyeing properties are the commercially available acrylic ester and vinylester type of compounds. In fibres of this kind, however, in whichcrimping is due to equalisation of the shrinkage tension, the stabilityunder thermal or hydrothermal stressis reduced, especially if higherporportions of comonomer are used in one of the polymers. This reducedstability has the effect, for example, ofimpairing the development ofbulk when dyeing the textiles.

It has now been found that a stable crimp which extends uniformlythroughout the yarn may be obtained by using composite fibres ofacrylonitrile polymers which contain a substantially equivalent numberof acidic groups, but in which varying proportions of acrylic ester orvinyl ester type comonomers are incorporated by polymerisation.

It is therefore an object of the invention to provide textile fibreswhich develop a stable and uniformly extending crimp.

Other objects will be evident from the description and the Examples.

These objects are accomplished by a spontaneously crimping compositefibre comprising at least two different acrylonitrile polymers whichhave substantially the same acidic group content, produced in aside-by-side arrangement of the two fibre-forming components inproportions, by weight, of from 40:60 to 60:40, one of the fibre-formingcomponents containing up to 6%, by weight, of at least one copolymerisedester while the quantity of said copolymerised ester in the otherfibreforming component is from 2 to 6%, by weight, higher, saidcopolymerised ester being methyl acrylate and/or isobutene diacetate(Z-methylenepropanel ,3- diacetate), under the condition that at leastone of the fi'breforming components contains at least 2%, by weight,isobutene diacetate and the total quantity of said copolymerised estersin one fibre-forming component does not exceed 12%, by weight.

A further object of this invention is a yarn or a textile article whencontaining such a fibre.

The second fibre forming component may also be produced from severaldifferent polymers provided that the mixture has the total ester contentindicated above. The nature and quantity of additional copolymerisedacidic dye additives in the fibre-forming component is not criticalprovided it is within the range of from 0.5 to 6%, by weight, and thatthe equivalent contents are approximately equal.

If composite fibres containing isobutene diacetate as comonomer andhaving the compositions indicated above are produced by a dry-spinningprocess in which two streams of fibre-forming polymer solutions in asolvent, such as dimethylformamide, are brought together in spinningdies in such a manner that composite fibres are obtained in aside-by-side arrangement and these spun fibres are then treated by theconventional processes, then three-dimensionally crimped fibres areobtained which may be worked-up into yarns in conventional textilemachines. When such yarns are dyed in hanks, for example, they developexcellent bulk and elasticity after drying without any thin patches orcolour irregularities in the plied yarns. Once the crimp has developedin the fibre, it is not diminished by subsequent wet treatments andknitted textiles manufactured from these yarns therefore remaindimensionally stable after washing and retain their gloss which is dueto the intensity of crimping.

Whereas the'irreversibility of the crimp in the fibres was deliberatelyachieved according to the invention by choosing fibre-forming componentswhich contain equal amounts of acidic groups, the stability of the crimpdiscovered in the new composite fibres containing isobutene diacetatecomonomer was unexpected.

If, for example, a bicomponent fibre is spun from equal parts ofcopolymers of acrylonitrile with methyl acrylate and-with sodiummethallylsulphonate, which copolymers have the same sulphonate contentbut differ from each in their ester contents which are 5.6% and 9.0%, byweight, respectively, and if yarn produced from such a bicomponent fibreis hank dyed, it is found that distributed over the circumference of thehank there are strands of yarn of unequal or varying thickness andcolour which prohibits the use of such yarn for fine quality knitwear.If, on the other hand, a yarn is produced under similarconditions fromthe following fibre-forming components:

A. 93.4% "acrylonitrile, 5.6% methylacrylate, 1.0%

sodium methallylsulphonate; and

B. 90.5% acrylonitrile, 8.5% isobutene diacetate,

1.0% sodium methallysulphonate, then it is surprisingly found that thedyed yarn is very uniform in thickness, colour and elasticity andknitted goods produced from it have an attractive appearance and goodwearing qualities.

Composite fibres with equally stable crimp may be obtained from acombination of acrylonitrile polymers which contain from 2 to 6%, byweight, of a vinyl or acrylic ester compound with copolymers which inaddition to from 2 to 6%, by weight, of vinyl or acrylic ester compoundscontain from 3to 6%, by weight, isobutenediacetate calculated so thatthe total quantity of ester comonomers in the last mentioned copolymerdoes not exceed 12%, by weight.

Lastly, composite fibres obtained from a combination of acrylonitrilepolymers which contain from 2 to 6% by weight, of a vinyl or acrylicester compound and polymer mixtures which contain a total of from 2 to6% by weight, of a vinyl or acrylic ester and in addition from 3 to 6%by weight, of isobutene diacetate in this mixture also fulfill thepurposes of this invention.

Copolymers of acrylonitrile with isobutene diacetate and optionallyother copolymerisable monomers may be obtained in high yields by theprocess of redox polymerisation in an aqueous medium at pH values offrom 2 to 7 and temperatures of from 0 to C with the aid of peroxycompounds and sulphur compounds in a lower oxidation state preferablyusing a ratio of activator to catalyst of 5:1. Examples of suitablecopolymerisable compounds include the lower vinyl and acrylic esters,such a vinyl acetate and methyl acrylate, unsaturated sulphonic acids,such as methallylsulphonic acid or its salts, acrylic or vinyl compoundswhich contain neutral or basic groups, such as acrylamide,allylurethane, N-vinylpyrrolidone, and N,N-drnethylaminoethyl-methacrylate. There is no restriction to the use ofparticular comonomers provided they may be incorporated in the desiredacrylonitrile polymers in economically acceptable yields. Copolymerscontaining from 3 to 30%, by weight, of isobutene diacetate weresuccessfully prepared according to the invention.

The polymers obtained in this way were spun by a dry-spinning processfrom dimethylformamide solutions of a suitable concentration forspinning. Suitable designed nozzles were used so that the fibre-formingcomponents were united side-by-side shortly before discharge from thedie aperture in predetermined proportions which were identical for allfibres and were then coagulated in this permanently united form toproduce filament bundles which could be drawn off. The selected ratio offibre-forming components may be from 75:25 to 25:75, the best crimpingproperties in the finished fibres being obtained in the region of from60:40 to 40:60 and most preferably about 50:50.

It is well known to one skilled in the art to produce similar compositefibres in which the distribution of components varies from fibre tofibre or to produce fibres with a sheath and core or multilayeredarrangement. Furthermore, spinning of composite polyacrylonitrile fibresaccording to this invention is of course not restricted to the solventreferred to herein or to the dryspinning technique. Various conventionalprocesses are available for producing textile fibres from dry-spun goodsof the type described above, from which the most suitable may beselected according to the subsequent textile processes which are to beapplied to the fibres. If, for example, the fibres are to be processedin worsted spinning or cotton spinning machines, it is most suitable toproduce completely shrunk fibres with fully developed crimp. If, on theother hand, the fibres are to be torn up as cable yarns in aturbostapler or converting machine, it is advantageous to prepare themin the form of bands which are in a potentially crimpable state because,in this case, the proper crimp is developed only in the end-product bysteaming or dyeing. The composite fibres according to this inventionmay, of course, also be spun together with other completely shrunk orstill shrinkable natural or synthetic fibres, and the fibrous productsobtained by tow processing in suitable machines may also be worked-up incombination with other fibre products in various ways.

The yarns obtained from processing pure fibres according to thisinvention are distinguished by their wool-like bulk and hand, clearsurface structure, high elasticity and springiness and uniformity ofyarn. These qualities are not impaired by wear and repeated washing oftextile fabrics produced from these yarns, and the dimensional stabilityof such products is very satisfactory.

The fibres according to the invention are therefore also suitable foraddition to other natural or synthetic fibres in which by virtue oftheir own permanent crimp they substantially improve such qualities asthe bulk, hand and springiness as well as the pilling properties of thefinished articles.

EXAMLPES In the following Examples, which are to further illustrate theinvention without limiting it, the figures given for the polymercompositions and concentrations are percentages by weight.

The criterion adopted for determining the stability of the crimp was inall cases the uniformity of worsted yarn after it has been hank dyed atC and dried at 80C. Fibres which developed their bulk in the compositeyarn without significant fluctuations in thickness or elastivity wereclassed as crimp stable.

EXAMPLE 1 Copolymers of the composition A. 93.4% acrylonitrile, 5.6%methylacrylate, 1.0%

sodium methallylsulphonate; and

B. 90.5% acrylonitrile, 8.5% isobutenediacetate,

1.0% sodium methallylsulphonate were used to prepare dimethylformamidesolutions with solid contents of 28.6% and 25.8% respectively. Thesesolutions were spun in equal parts (by volume) through ring-shapedspinning nozzle with 180 apertures as side-by-side composite fibres at adraw-off rate of 250 m/min. The fibres were coagulated with hot air andwound on to spools. They had a curved dumb-bellshaped cross-section andstill contained 22.6% dimethylformamide.

Several spinning spools were combined and streached to 1:40 in boilingwater and then washed. The tow obtained in this way was covered with anapplication of oil, dried under tension, crimped in a compressionchamber and cut to a staple length of about mm, and the staple fibreswere shrunk by steaming and dried. The fibres at that stage stillcontained 0.4% dimethylformamide and after boiling and drying at 80Cthey had 13.4 crimps per cm of stretched length. Their thickness was 3.0dtex, their tensile strength 2.55 g/dtex and their elongation at break44%.

When hank dyed, the worsted yarn (Nm 16/4) of these fibres shrunk by9.3% and gave rise to a yarn which had a full bulk and firm hand and wascompletely uniform when plied.

EXAMPLE 2 Copolymers composed of C. 91.7% acrylonitrile 7.5% isobutenediacetate,

0.8% sodium methallylsulphonate; and D. 93.8% acrylonitrile, 5.5%methylacrylate, 0.6%

sodium methallylsulphonate were used as described in Example lto preparedimethylformamide solutions at concentrations of 27.5% and 28.3%respectively. The solutions were spun to composite fibres with adumb-bell-shaped cross section and a residual solvent content of 17.3%.By aftertreating the fibres in a similar way as described in Example 1,except that a stretching ratio of 1:3.6 was employed, fibres with aresidual dimethylformamide content of 0.8% and a crimp number (afterboiling and drying) of 10.4/cm were obtained. The titre was 4.3 dtex,the tensile strength 2.34 g/dtex and the elongation at break 49%.

A worsted yarn (Nm l6/4) of these fibres had a boiling shrinkage in theraw state of 5.0%, and when hank dyed it developed an excellent bulkwith a pearly appearance on the surface of the yarn and uniformity ofthe individual strands.

EXAMPLE 3 Equal parts, by volume, of a 27.4% solution in dimethylformamide of a polymer E. 94.0% acrylonitrile, 5.0% isobutenediacetate,and

1.0% sodium methallylsulpnonate; and of the 29.4% solution of a polymerF. 90.5% acrylonitrile 8.5% isobutenediacetate and 1.0% sodiummethallysulphonate were spun through a spinning die, as described inExample l, to produce composite fibres with a dumbbell-shaped crosssection and a solvent content of 17.5%. The fibres were stretched by123.6 in boiling water, washed, brightened, dried, cut to a length ofabout 1 mm and shrunk by streaming at normal pres sure. The residualsolvent content was 1.4%, the crimp number, after boiling and drying,9.9/cm the titre 3.7 dtex, the tensile strength 2.54 g/dtex and theelongation at break 46%.

A fibre yarn of a thickness used for hand knitting (Nm 16/4) was hankdyed, and after a yarn shrinkage of 7.4% it had a bulky, pleasantly softand elastic handle without pressure points or thickenings in the yarn.

EXAMPLE 4 Copolymers of the following compositions G. 88.2%acrylonitrile, 5.0% isobutene diacetate,

5.8% methylacrylate, 1.0% sodium methallysulphonate; and

H. 93.4% acrylonitrile, 5.6% methylacrylate, 1.0%

methacroylaminobenzene-benzenedisulphonimide; were used as described inExample 1 to prepare 28.1% and 28.7% solutions, respectively. Thesesolutions were spun through a spinning die with 120 apertures to producecomposite fibres with a solvent content of 20.0% and a lobedcross-section. The fibres were stretched by 1:37 in water at 98C, driedunder tension, sprayed with dressing and shrunk by steaming in the formof a mechanically crimped tow. The residual solvent content at thatstage was 0.3% and the crimp number, after boiling and drying, wasl5.7/cm, The titre of the individual fibres was 2.9 dtex, the tensilestrength 2.35 g/dtex and the elongation on break of 34%.

After cutting up into staple fibres, a yarn (Nm 16/4) was spun and hankdyed as described above. The yarn shrinkage was 10.6%. The yarn had highbulk and a springy elasticity and the plied yarn had a uniformthickness.

COMPARISON EXAMPLE The experiment shows that the crimping properties ofa fibre are insufficient for practical purposes if there is too littledifference in the ester content between the fibre-forming components.The components used to prepare a side to side composite fibre, asdescribed in Example 1, were the polymers J. 94.2% acrylonitrile, 5.0%isobutene diacetate,

0.8% sodium methallylsulphonate, and K. 93.25% acrylonitrile, 5.75%methylacrylate, 1.0% methacroylaminobenzene-benzenedisulphonimide. Thesepolymers were used as 27.4% and 28.6% dimethylformamide solutionsrespectively. The solutions were spun in equal parts, by volume, througha spinning die of the type described above to form fibres with abean-shaped cross-section and a solvent content of 14.1%. The shrunkfibres produced from these fibres by stretching by 1:4.6 still had aresidual dimethylformamide content of 0.2%, a titre of 3.1 dtex, atensile strength of 3.15 g/dtex, an elongation on break of 33% and acrimp number after development of 5.8/cm.

When a worsted yarn (Nm 16/4) of this product was hank dyed in a singlebath together with other samples of yarn it shrunk by 4.1% and had a lowbulk, was marked by pressure points and had little elasticity and a poorhand.

EXAMPLE 5 In accordance with Example 1, 28.0% and 26.7% solutions of thecopolymers L. 89.0% acrylonitrile, 10.0% isobutenediacetate,

1.0% sodium methallylsulphonate; and M. 99.4% acrylonitrile 0.6% sodiummethallysulphonate, were spun through 120 aperture dies to producecomposite fibres which contained 22.0% dimethylformamide and had amushroon-shaped or lobular crosssection. Further treatment was carriedout as described in Example 1, to produce fibres with a residual solventcontent of 1.2% and a crimp number of 16.3/cm. The titre was 3.0 dtex,the tensile strength 2.18 g/dtex and the elongation on break of 35%.

l-lank dyeing resulted in an exceptionally high bulk worsted yarn (Nm16/4) which had shrunk by 12.6% and had a high elasticity of elongationand uniform thickness in the plied thread.

EXAMPLE 6 The following polymers N. 93.3% acrylonitrile, 5.7% methylacrylate, 1.0%

methacroylaminobenzene-benzene disulphonimide; and

O. 70.0% acrylonitrile, 30.0% isobutenediacetate, were used to prepare amixture of (N) and 20% (O) which was spun as a 27.5% dimethylformamidesolution, together with a 28.3% solution of polymer (N), through a 120aperture die to produce a composite fibre in the manner described above.The solvent content of the spinning material was 17.0%. The fibres has aclub-shaped" profile. Staple fibres mm in length were produced asdescribed in Example 1. They had a residual solvent content of 1.5%. thetitre of the fibres was 5.4 dtex, the tensile strength 2.31 g/dtex, theelongation on break of 48% and the crimping 15.4 arcs/cm.

A worsted yarn (Nm 16/4) of the fibre had a shrinkage of 9.7%. The hankdyed sample had a very high bulk, springiness and elongation elasticityand a woolly hand without pressure points or stretching points.

When side-by-side composite fibres were produced from about half andhalf of polymers (N) and (O), nodular cross-sections were obtained, andfibres which had received the same after-treatment had a very tightcrimp which made further textile operations impossible.

EXAMPLE 7 Using polymers of the following compositions P. 93.3%acrylonitrile, 5.7% methylacrylate, 1.0%methacroylaminobenzene-benzenedisulphonimide; and O. 78.5% acrylonitrile23.0% isobutene diacetate,

1.0% sodium methallylsulphonate, a 28.7% dimethylformamide solution of(P) was dryspun with a 26% solution of a mixture of 75% (P) and 25% (Q)through a 120 aperture die of the type described above at a draw-offrate of 250 m/min to produce a composite fibre. The spinning fibrescontained 12.5% solvent and had a dumb-bell-shaped crosssection.

Completely shrunk fibres with a dtex of 3.3 were pro duced as describedin Example 3. The residual solvent content was then 0.5% and the crimpnumber, after boiling and drying 10.3/cm.

A fibre yarn (Nm 16/4) was hank dyed and shrunk by 13.1%. A yarn with afull hand and uniform bulk was obtained. A knitted fabric produced fromthis yarn was distinguished by its exceptional clarity and coveringpower of the stitches. The character of the fabric was unchanged aftermachine washing.

EXAMPLE 8 Equal parts by volume, of 28.5% dimethylformamide solutions ofthe fibre-forming components R. 93.3% acrylonitrile, 5.7%methylacrylate, 1.0%

methacroylaminobenzene-benzenedisulphonimide; and

S. 90.15% acrylonitrile, 9.25% isobutene diacetate,

0.6% sodium methallylsulphonatc were dry-spun through tubular dies with240 apertures to produce fibres with a residual solvent content of 19.6%and a bean-shaped to trilobular cross-section. The spinning bands werestretched by 124.5 in boiling water, washed, brightened, dried with 20%shrinkage, crimped in compression chambers and laid off as tows with atotal weight of 27 g/m. The solvent content was then 0.7%, the remainingboiling shrinkage 5.4%, the titre 3.4 dtex, the tensile strength 3.0g/dtex, the elongation on break of 33% and the crimp number afterdevelopment 4.1/cm.

This material, combined in the form of a band weighing 54 g/m wasprocessed into a spinning band in a Seydel converting machine (type 633)with 30% elongation and a hotplate temperature of 180C. After steamingunder pressure, the spinning band was processed into a fine yarn (Nm30/2). When hank dyed, this yarn again shrunk by 9.6% and had excellentbulk and elongation elasticity and worked-up into a knitted fabric withclear, uniform stitches.

When the spinning band was directly made up into a yarn of the samenumber without steaming, the shrinkage in the dye bath was 28.2% andresulted in an unacceptably tight, rough thread.-

We claim:-

1. A spontaneously crimping composite fibre comprising at least twodifferent acrylonitrile polymers which have substantially the sameacidic group content, produced in a side-by-side arrangement of the twofibre-forming components in proportions, by weight, of from 40:60 to60:40, one of the fibre-forming components containing up to 6%, byweight, of at least one copolymerised ester while the quantity of saidcopoly merised ester in the other fibre-formingcomponent is from 2 to6%,-by weight, higher, said copolymerised ester being methyl'acrylateand/or isobutene diacetate (-2-methylenepropane-1,3-diacetate), underthe condition that at least one of the fibre-forming components containsat least 2%, by weight, isobutene diacetate and the total quantity ofsaid copolymerised esters in one fibre-forming component does not exceed12%, by weight.

2. The spontaneously crimping composite fibre of claim 1, in which bothfibre-forming components contain isobutene diacetate, one componentcontaining from 2 to 6% by weight, thereof more thanthe other and thetotal isobutene diacetate content based on the one fibre-formingcomponent, not exceeding 12%, by weight. I

3. vThe spontaneously crimping composite fibre of claim 1, in which oneof said fibre-forming components contains from 0to 6%, by weight, methylacrylate and the other up to 12%, by weight, isobutene diacetate, thequantitative difference in the ester content between said two componentsbeing atleast 2%, by weight.

4. The spontaneously crimping composite fibre of claim 1, in which bothfibre-forming components contain from 2 to 6% methyl acrylate and one ofsaid fibreforming components in addition contains from 3 to 6%, byweight, isobutene diacetate.

5. A yarn or a textile article produced from the composite fibre ofclaim 1.

1. A SPONTANEOUSLY CRIMPING COMPOSITE FIBRE COMPRISING AT LEAST TWODIFFERENT ACRYLONITRIL POLYMERS WHICH HAVE SUBSTANTIALLY THE SAME ACIDICGROUP CONTENT, PRODUCED IN A SIDE-BY SIDE ARRANGEMENT OF THE TWOFIBRE-FORMING COMPONENTS IN PROPORTIONS, BY WEIGHT, OF FROM 40-60 TO60:40, ONE OF THE FIBRE-FORMING COMPONENTS CONTAINING UP TO 6%, BYWEIGHT, OF AT LEAST ONE COPOLYMERISED ESTER WHILE THE QUANTITY OF SAIDCOPOLYMERISED ESTER IN THE OTHER FIBRE-FORMING COMPONENT IS FROM 2 TO 6%BY WEIGHT, HIGHER, SAID COPOLYMERSED ESTER BEING METHYL ACRYLATE AND/ORISOBUTENE DIACETATE (2METHYLENEPROPANE- 1,3-DIACETATE ), UNDER THECONDITION THAT AT LEAST ONE OF THE FIBRE-FORMING COMPONENTS CONTAINS ATLEAST 2% BY WEIGHT ISOBUTENE DIACETATE AND THE TOTAL QUANTITY OF SAIDCOPOLYMERISED ESTERS IN ONE FIBRE-FORMING COMPONENT DOES NOT EXCEED 12%,BY WEIGHT.
 2. The spontaneously crimping composite fibre of claim 1, inwhich both fibre-forming components contain isobutene diacetate, onecomponent containing from 2 to 6% by weight, thereof more than the otherand the total isobutene diacetate content based on the one fibre-formingcomponent, not exceeding 12%, by weight.
 3. The spontaneously crimpingcomposite fibre of claim 1, in which one of said fibre-formingcomponents contains from 0to 6%, by weight, methyl acrylate and theother up to 12%, by weight, isobutene diacetate, the quantitativedifference in the ester content between said two components being atleast 2%, by weight.
 4. The spontaneously crimping composite fibre ofclaim 1, in which both fibre-forming components contain from 2 to 6%methyl acrylate and one of said fibre-forming components in additioncontains from 3 to 6%, by weight, isobutene diacetate.
 5. A yarn or atextile article produced from the composite fibre of claim 1.